1. Field of the Invention
The invention relates to a process for estimating the distance between a stationary object, for example the ground, and a moving vehicle, for example an aircraft, by using a series of images analyzed by a sensor mounted on the vehicle. If these images are centered in the direction of movement of the vehicle, any object grows from one image to the next, as the vehicle approaches the object, then disappears by leaving the image when the vehicle passes from the vicinity of the object. The size of the image of the object and its position in the analyzed image vary continuously as a function of the distance of the vehicle from the object.
2. Discussion of Background
Known processes make it possible to estimate the distance between a stationary object and a vehicle on which an image sensor is mounted. These known processes have the common characteristic of using a spatial differentiation of images to show the contours of objects. The movement of the contours then makes it possible to evaluate the speed of the various objects present in the image. The speed field thus determined makes it possible to estimate the distance to the vehicle.
The known processes are very sensitive to noise because they use an image spatial differentiation to show the contours of the objects, with a subsequent differential processing to show the movements of the contours. These two successive differentiations favor high spatial and time frequencies so that the signal-to-noise ratio is greatly affected. They are therefore particularly ill-suited for very noisy images such as images provided by an infrared camera. Furthermore, the image spatial differentiation of the prior art has difficulty finding contours which consists of fine transitions. Finally, the determination of contours in each image requires many calculations, which are difficult to perform in real time.